Dual Tone Multi Frequency (DTMF) tones comprise tones developed for the Public Switched Telephone Network (PSTN), wherein each telephone key produces a unique DTMF tone when pressed. A DTMF tone comprises two tones of specific frequencies. The DTMF system uses eight different frequency signals that are transmitted in pairs to represent 16 different numbers, symbols, and letters.
The DTMF system was originally developed to be included in-band with the telephone voice signal. However, in current systems the DTMF tones may be included in-band, along with a voice call or audio, or may be transmitted out-of-band.
A DTMF circuit may receive an audio signal including DTMF tones or digits. The DTMF circuit may need to relay the DTMF digits, such as to other communication devices or components. In some circumstances, when the DTMF device transfers a DTMF digit to a receiving DTMF device, the DTMF device may incorrectly receive more than one DTMF digit. This may be more likely if the received DTMF digit has been previously transcoded or otherwise processed. The incorrect reception of a DTMF digit or digits may lead to incorrect operation of the device or devices receiving the DTMF digits.